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Maize regulatory gene opaque-2 encodes a protein with a "leucine-zipper" motif that binds to zein DNA. (1990)

Schmidt, R. J. ; Burr, F. A. ; Aukerman, M. J. ; [et al.]

National Academy of Sciences

In: PNAS - Proceedings of the National Academy of Sciences of the United States of America. 1990; 87(1): 46-50. Published 1990 Jan 01. doi: 10.1073/pnas.87.1.46.

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Publication Date: 1990-01-01

Print ISSN: 0027-8424

Electronic ISSN: 1091-6490

Topics: Biology , Medicine , Natural Sciences in General

Published by National Academy of Sciences

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Contribution of collagen and mineral to the elastic anisotropy of bone (1994)

Hasegawa, K. ; Turner, C. H. ; Burr, D. B.

Springer

Calcified tissue international 55 (1994), S. 381-386

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ISSN: 1432-0827

Keywords: Acoustic microscopy ; Bone ; Collagen fiber ; Elastic anisotropy ; Mineral crystal

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine , Physics

Notes: Abstract It has long been thought that collagen fibers within the bone matrix are deposited in an aligned pattern that channels mineral growth. If this model of bone structure is correct, both organic and inorganic phases of bone should have similar elastic anisotropy. Using an acoustic microscope, we measured longitudinal and transverse acoustic velocities of cortical specimens taken from 10 dog femurs before and after removal of either the mineral (using 10% EDTA) or collagen phases (using 7% sodium hypochlorite) and calculated longitudinal (CL) and transverse (CT) elastic coefficients. The anisotropy ratio (CL/CT) decreased significantly after demineralization (1.61 before versus 1.06 after, P〈0.0001, paired t-test). However, there was no significant change after decollagenization (1.51 before versus 1.48 after, P=0.617, paired t-test). We conclude that the orientation of mineral crystals is the primary determinant of bone anisotropy, and the collagen matrix within osteonal bone has little directional orientation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00299319

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Remodeling and the repair of fatigue damage (1993)

Burr, David B.

Springer

Calcified tissue international 53 (1993), S. S75

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ISSN: 1432-0827

Keywords: Microdamage ; Remodeling ; Fatigue ; Osteoporosis

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine , Physics

Notes: Summary This paper reviews the direct and indirect evidence for and against the idea that bone remodeling repairs fatigue damage. It defines experiments that should be performed to determine whether the accumulation and repair of fatigue damage is relevant to the pathogenesis of osteoporotic fracture. The experimental evidence favors the hypothesis that microdamage evokes local remodeling. The data suggest that the balance between the microdamage burden and bone repair is nearly constant. The indirect evidence comes from clinical observations that show positive relationships between depressed bone formation rate or prolonged remodeling period with bone fracture. More compelling indirect evidence comes from studies in which bone remodeling was pharmaceutically depressed, and fracture incidence rose in direct proportion. Data on microdamage accumulation were not collected in these studies. Conversely, some experimental evidence disputes a direct relationship between fatigue microdamage and repair. In these studies, increased amounts of bone microdamage in hyperadrenocortical dogs, and in irradiated dogs, could not be demonstrated even though bone fragility increased without associated osteopenia. Finally, the indirect evidence that argues that microdamage does not initiate repair is based on inference and does not provide an adequate test of the hypothesis. In balance, the current body of evidence favors the contention that bone remodeling repairs fatigue damage and thereby prevents fracture. Future studies should verify that microdamage accumulates when bone fracture occurs in conjunction with depressed remodeling activation frequency.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01673407

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Scanning motion, ocellar morphology and orientation mechanisms in the phototaxis of the nematode Mermis nigrescens (1990)

Jay Burr, A. H. ; Babinszki, Colette P. F.

Springer

Journal of comparative physiology 167 (1990), S. 257-268

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ISSN: 1432-1351

Keywords: Scanning motion ; Shadowing ; Ocellus ; Mechanism ; Orientation ; Phototaxis ; Klinotaxis ; Photomovement ; Transverse phototaxis ; Nematode

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary The putative ocellus of Mermis females consists of a hollow cylinder of dense hemoglobin pigmentation located in the anterior tip. The exact location of the photoreceptive nerve endings, however, is unknown. During phototaxis a continual bending or scanning motion of the head (anterior 2 mm) causes the orientation of the tip to swing about the direction of the source. By turning off (shuttering) the light source whenever the tip orientation was to one side of the source direction, the average orientation of the base of the head, and eventually the body orientation, was caused to be biased about 28° to the opposite side. Because the shuttering was synchronized with the scanning motion, the scanning motion must be involved in the maintenance of orientation to light. The direction of the bias rules out a two-signal comparison mechanism of orientation and demonstrates that a deviation of the tip from the source direction must decrease, rather than increase, the illumination of the photoreceptors. These findings, and the ocellar morphology, require that the photoreceptors be located inside the hollow tube of pigmentation where they can be shadowed by the pigment during deviations of the tip. Focusing by the curved anterior end should cause a similar modulation of the illumination at this location. The occasional episodes of transverse phototaxis can be explained by the leakiness of the pigment walls to transverse illumination. Analysis of the motion of the anterior in the presence and absence of shuttering indicates that the orientation of the base of the head, due to the motion of the neck, is controlled by the signals generated during one or more cycles of the scanning motion of the head. The orientation may be regulated by the phase relationship between the photoreceptor signal and putative proprioceptive signals that indicate the bending in the head.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00188118

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Components of phototaxis of the nematode Mermis nigrescens (1990)

Burr, A. H. Jay ; Babinszki, Colette P. F. ; Ward, Amanda J.

Springer

Journal of comparative physiology 167 (1990), S. 245-255

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ISSN: 1432-1351

Keywords: Undulatory locomotion ; Scanning motion ; Directed turn ; Orientation ; Phototaxis ; Klinotaxis ; Photomovement ; Nematode

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary The gravid females of Mermis are positively phototaxic at the time of their migration to egglaying sites in vegetation on which their grasshopper hosts feed. On a horizontal felt surface, segments of the path traced by the tail are oriented approximately towards a source of monochromatic light in the 350–540 nm region, but are not oriented at longer wavelengths and in the dark. The components of this phototaxis include locomotion by the posterior 4/5 of the body, orientational bending of the neck region while the anterior is held above the substrate, and a scanning motion (bending) of the head region (anterior 2 mm). Like other nematodes and snakes, propulsion is associated with posteriorly propagated body waves, but unlike other animals known, the waves tend to lie perpendicular to a felt surface, and unlike other nematodes, contact with the surface is on the female's ventral surface. The body waves are initiated by the motion of the anterior 1/5 (15 mm) of the body, the average orientation of which determines the path of the following 4/5. During phototaxis, the anterior tip is swung both sideways and vertically about the direction towards the light source. The tip motion is a result of a scanning motion of the head and a slower orientational bending of the neck. The base of the head appears to be actively directed towards the source by the bending of the neck. This behavior can resolve two light sources positioned 120° apart but not 90° apart. The scanning motion of the head is independent of neck orientation and appears to enhance the probability of discovering the direction of a new source. Discovery is followed by a directed turn of the base of the head towards the source which is initiated by the bending of the neck. Locomotion of the body follows the path of the anterior through the turn and phototaxis is thus initiated.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00188117

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Lead exposure from conventional and cottage lead smelting in Jamaica (1991)

Matte, Thomas D. ; Figueroa, J. Peter ; Ostrowski, Stephanie ; [et al.]

Springer

Archives of environmental contamination and toxicology 21 (1991), S. 65-71

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ISSN: 1432-0703

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine

Notes: Abstract A survey was conducted to determine the distribution and determinants of environmental and blood lead levels near a conventional and several cottage lead smelters and to assess the relationship between environmental and blood lead levels in a tropical, developing-country setting. Fifty-eight households were studied in the Red Pond community, the site of the established smelter and several backyard smelters, and 21 households were studied in the adjacent, upwind Ebony Vale community in Saint Catherine Parish, Jamaica. Households were investigated, using questionnaires, soil and housedust lead measurements, and blood lead (PbB) measurements from 372 residents. Soil lead levels in Red Pond exceeded 500 parts per million (ppm) at 24% of households (maximum-18,600 ppm), compared to 0% in Ebony Vale (maximum 150 ppm). Geometric mean PbB in Red Pond, where 44% of children 〈6 years of age had PbB levels ≥ 25 micrograms per deciliter (μg/dL), was more than twice that Ebony Vale in all age groups (p 〈 0.0005). Within Red Pond, proximity to backyard smelters and to the conventional smelter were independent predictors of soil lead (p 〈 0.05). Soil lead was the strongest predictor of PbB among Red Pond subjects under 12 years of age. The blood lead-soil lead relationship in children differed from that reported in developed countries; blood lead levels were higher than expected for the household-specific soil lead levels that were observed. These data indicate that cottage lead smelters, like conventional ones, are a hazard for nearby residents and that children exposed to lead contamination in tropical, developing countries may be at higher risk for developing elevated blood lead levels than similarly-exposed children in developed countries.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01055558

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Sequence, identification and characterization of cDNAs encoding two different members of the 18 kDa heat shock family of Zea mays L. (1991)

Goping, Ing Swie ; Frappier, J. Roger H. ; Walden, David B. ; [et al.]

Springer

Plant molecular biology 16 (1991), S. 699-711

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ISSN: 1573-5028

Keywords: heat shock ; heat shock cDNAs ; maize ; small heat shock proteins

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Heat-shocked maize seedlings (cv. Oh43) synthesize a characteristic set of heat-shock proteins (hsps) which include an 18 kDa family containing at least six major isoelectric variants. A cDNA library was constructed from poly(A)+ RNAs isolated from the radicles of heat-shocked maize seedlings and screened with a DNA fragment from the theoretical open reading frame of a putative Black Mexican Sweet maize hsp 18 genomic clone. Two clones, cMHSP18-3 and cMHSP18-9, were isolated, and the RNA transcripts generated from them were translated into proteins which immunoreact with antibodies directed against the maize 18 kDa hsps and exhibit the same electrophoretic characteristics as two different members of the 18 kDa hsp family. Nucleotide sequence analyses of the cDNAs in these clones reveal that their 5′ and 3′ untranslated regions exhibit 33–34% identity and that their protein encoding regions share 93% identity. The deduced amino acid sequences of these clones show 90% identity, and the apparent molecular masses and isoelectric points of these proteins agree with those established for two different 18 kDa hsps, numbered 3 and 6. This report substantiates that at least two of the 18 kDa hsps in maize are products of different but related genes. Moreover, it establishes that transcripts for these proteins accumulate during heat shock and that both their nucleotide and deduced amino acid sequences share extensive similarities with the class VI small hsps in soybean and with transcripts expressed during meiosis in Lilium.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00023434

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Characterization of zoospore and cyst surface structure in saprophytic and fish pathogenicSaprolegnia species (oomycete fungal protists) (1994)

Burr, A. W. ; Beakes, G. W.

Springer

Protoplasma 181 (1994), S. 142-163

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ISSN: 1615-6102

Keywords: Saprolegnia ; Lectins ; Concanavalin A ; Wheat germ agglutinin ; Monoclonal antibodies ; Ultrastructure ; Pathogenesis

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The importance of the surface structure and chemistry in zoospores and cysts of oomycetes is briefly reviewed and the organelle systems associated with encystment described. The surface structure and chemistry of primary and secondary zoospores and cysts ofSaprolegnia diclina (a representative saprophytic species) andS. parasitica (a representative salmonid fish pathogen) were explored using the lectins concanavilin A (Con A) and wheat germ agglutinin (WGA) and monoclonal antibodies (MAbs) raised against a mixed zoospore and cyst suspension ofS. parasitica. The binding of lectins and antibodies to spores was determined using immunofluorescence microscopy with fluorescein isothiocyanate-labelled probes and with electron microscopy with gold-conjugated probes applied to spore suspensions post-fixation. In both species Con A, which is specific for glucose and mannose sugars, bound to both the surface of primary and secondary zoospores (the surface glycocalyx) and their cyst coats and readily induced zoospore encystment. The binding to the cysts appeared to be mainly associated with the matrix material released from the primary and secondary encystment vesicles and which appeared to diminish with time. No binding to germ tube walls was observed with this lectin. The MAb labelling showed a generally similar binding pattern to the primary and secondary cysts to that observed with Con A, although the binding to zoospores was more variable. Primary zoospores bound the antibodies but secondary zoospores appeared less reactive. It is suggested that the MAbs share a common epitope with one or more of the Con A-binding components. In both species WGA, which is specific for amongst other things the sugar N-acetyl glucosamine, bound to localised apical patches on the primary zoospores. This lectin also binds to the ventral groove region of secondary zoospores ofS. diclina, which were induced to encyst by this lectin. In contrast secondary zoospores ofS. parasitica were not induced to encyst by the addition of WGA and showed a patchy dorsal binding with this lectin. WGA also binds to both the inner wall of discharged primary cysts and the young germ tube walls of both species. These observations are discussed both in relation to other oomycete spores and to their possible functional and ecological significance.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01666393

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